The ability of an atom in a molecule to attract the shared electrons in a bond toward itself is called electronegativity.
Missing Word
electronegativity
Electronegativity measures how strongly a bonded atom pulls on shared electrons. Differences in it between two bonded atoms determine how polar the bond is.
Category: Bond Polarity
Question 2
A negatively charged ion, formed when a nonmetal atom gains electrons, is called an anion.
Missing Word
anion
An anion is an ion with more electrons than protons. Nonmetals such as chlorine and oxygen typically gain electrons to form anions like Cl- and O2-.
Category: Ionic Bonding
Question 3
When a sodium atom gives up its single valence electron, it becomes a positively charged ion called a cation.
Missing Word
cation
A cation has fewer electrons than protons and so carries a positive charge. Metals such as sodium tend to lose valence electrons to form cations like Na+.
Category: Ionic Bonding
Question 4
A filled valence shell of eight electrons around a main-group atom is called an octet.
Missing Word
octet
An octet is a set of eight valence electrons, the arrangement of the noble gases. Many main-group atoms form bonds until each is surrounded by an octet.
Category: Lewis Structures
Question 5
In a Lewis structure, a bonded hydrogen atom is surrounded by just 2 valence electrons.
Missing Word
2
Hydrogen's valence shell is the 1s orbital, which holds only 2 electrons. A hydrogen atom in a molecule therefore forms one bond and has no lone pairs.
Category: Lewis Structures
Question 6
When no single Lewis structure describes a species and its true structure is an average of several electron arrangements, the species is said to exhibit resonance, shown with a double-headed arrow between the structures.
Missing Word
resonance
Resonance describes a species whose actual electron distribution is an average of two or more Lewis structures that differ only in electron placement. The real species is a single structure, not one that flips between forms.
Category: Formal Charge and Resonance
Question 7
A pair of equal and opposite partial charges separated by a distance, as found in a polar bond, is called a dipole.
Missing Word
dipole
A dipole is a separation of positive and negative charge. Its size, the dipole moment, depends on the magnitude of the charges and the distance between them.
Category: Molecular Polarity
Question 8
A molecule such as CCl4, whose bond dipoles cancel because of its symmetric shape, is described as nonpolar.
Missing Word
nonpolar
A nonpolar molecule has no net dipole moment. CCl4 has polar C-Cl bonds, but the tetrahedral arrangement makes their dipoles cancel.
Category: Molecular Polarity
Question 9
Breaking a chemical bond absorbs energy, so bond breaking is an endothermic process.
Missing Word
endothermic
An endothermic process takes in energy from the surroundings. Energy is always required to pull bonded atoms apart, so bond energies are positive values.
Category: Bond and Lattice Energy
Question 10
The direct change of a solid into a gas, which is the first step for the metal in a Born-Haber cycle, is called sublimation.
Missing Word
sublimation
Sublimation converts a solid directly to a gas without passing through the liquid. In a Born-Haber cycle the solid metal is first converted to gaseous atoms, which are then ionized.
Category: Bond and Lattice Energy
Question 11
The model that predicts molecular shape by assuming electron regions around a central atom arrange themselves as far apart as possible is abbreviated VSEPR.
Missing Word
VSEPR
VSEPR stands for valence shell electron-pair repulsion. It predicts geometry from the number of bonding and lone-pair regions around a central atom.
Category: Molecular Geometry
Question 12
The angle between electron regions in a trigonal planar arrangement is 120 degrees.
Missing Word
120
Three regions of electron density spread evenly in a plane, dividing the full circle into three equal parts of 120 degrees. BF3 is an example with this angle.
Category: Molecular Geometry
Question 13
A molecule such as CO2, with two bonding regions and no lone pairs on its central atom, has a linear shape.
Missing Word
linear
Two regions of electron density lie on opposite sides of the central atom, giving a linear arrangement with a 180 degree bond angle.
Category: Molecular Geometry
Question 14
The four C-H bonds of CH4 point to the corners of a regular four-faced solid, so the molecule is described as tetrahedral.
Missing Word
tetrahedral
Four regions of electron density point toward the corners of a tetrahedron, giving bond angles of 109.5 degrees.
Category: Molecular Geometry
Question 15
Six regions of electron density around a central atom, as in SF6, give an octahedral electron-pair geometry.
Missing Word
octahedral
Six regions arrange themselves along three perpendicular axes, pointing to the corners of an octahedron with 90 degree angles between neighbors.
Category: Molecular Geometry